SINGAPORE - An unemployed woman with a low IQ, anger management problems and other psychiatric issues was placed on probation in November last year for threatening and assaulting a woman and her two young sons.

But just six months later, Elizerbeth Chua Hui Ping, 26, grabbed a 10-year-old girl by the throat at Boon Lay Interchange.

Out on bail barely two weeks later, she choked a 14-year-old girl at the same interchange.

Both victims were unharmed.

Chua was jailed for nine weeks and fined $600 on Monday (Aug 29). She had pleaded guilty to three charges: committing public nuisance, causing hurt and behaving in a threatening manner towards a person. Two other similar counts were taken into account in sentencing.

A community court heard that Chua regularly accompanied her father when he went to work as an SBS Transit bus driver.

On May 23 this year, she saw a woman board her father's bus at Boon Lay interchange with a drink and got angry. She scolded the passenger, who threw the drink away before returning.

"However, (Chua) grew increasingly agitated and started shouting at commuters ... and challenged them to fight her, causing annoyance to the commuters," said Assistant Public Prosecutor Dillon Kok.

The mother of the 10-year-old girl asked Chua to calm down and lower her voice, as her daughter was getting frightened. Chua responded by choking the child.

The mother pushed Chua away and the girl ran out of the bus.

After the scuffle on the bus, Chua followed the mother as she left the bus and got into another scuffle with her until passers-by separated them.

Chua then spotted the girl and chased her around the interchange but the girl escaped by hiding. Chua was arrested and released on bail on June 7. The next day, she grabbed the 14-year-old girl at the same interchange. She also ran around the interchange threatening to bite others.

Chua had been placed on 18 months probation last year for slapping and pushing a six-year-old boy and his nine-year-old brother in Jurong West in December 2014 - because one of them had kicked a ball which narrowly missed her dog. She later threatened their 42-year-old mother, saying "I will beat and kill your sons", and punched and kicked her.

A government psychiatrist had found Chua to be oversensitive to criticism, impulsive and to have had anger management issues since she was young. She was bullied and ridiculed in primary school for her personality and low intelligence. She is on long-term psychiatric and psychotherapy treatment.